1. Technical Field
This disclosure generally relates to ultrasound probes, and more particularly to ultrasound probes having volume scanning capabilities and methods of using ultrasound probes for diagnostic purposes, such as, for example, determining bladder volume.
2. Description of the Related Art
Traditional three-dimensional (C-mode) ultrasound has been accomplished by sweeping a single scanline through target tissue with some combination of mechanical and electronic beam formation. For example, one method is to use a two-axis mechanical stepper motor configuration to move a single piston transducer. Other approaches have been to use electronic B-mode scanheads and add a single motor or a human operator to address the third dimension. Still another approach is to use a full up three dimensional electronically steered phased-array transducer.
Since ultrasound is a pulse-echo technology, the frame rate is limited by the transit time of the pulse-echo cycle. This constraint on frame rate can become overly restrictive as desired resolution increases and even more so when moving from two dimensional (B-mode) to three dimensional (C-mode) imaging. Reduced frame rates increase the likelihood of image blurring from operator movement, patient movement or patient anatomical movement, such as, for example, blood flow or respiration.
For certain diagnostic methods, such as, for example, bladder volume measurements, a single piston transducer swept through spherical coordinates with a multi-angular stepper motor has been used for years. While reasonably inexpensive to manufacture, this topology suffers from several deficiencies that compromise the accuracy of obtained data. For example, with respect to bladder volume measurements, the volumetric resolution of the system typically decreases in both angular directions with depth. Further, bladders that are closer to the patient's skin surface have a much smaller probability of fitting within the total scan solid angle of the system. This is because the bladder is anatomically located beneath the pubic bone where smaller scan cone angles of the system (which are typically less than 90 degrees) are unable to reach. Still further, the center of the cone has redundant scan lines which create processing inefficiencies and increase the maximum ultrasound exposed tissue which may decrease safety to some extent. Further, with systems that utilize a two-axis mechanical stepper topology, the result is one of the slowest frame rates available which increases image blurring and hence measurement accuracy. The combined effect of these deficiencies is an increased reliance on operator training and proper aiming of ultrasound imaging devices.
Consequently, Applicant believes improved diagnostic ultrasound imaging probes and methods are desirable. The ultrasound probes should be easier to aim and use to obtain accurate imaging results for diagnostic purposes. The ultrasound probes should also have a small, robust form factor or package.